Synergistic anti-microbial compositions comprising 2-bromo-2-(bromomethyl)-glutaronitrile and 2-bromo-2-nitro-propane-1,3-diol

ABSTRACT

This invention relates to methods and compositions for obtaining synergistic anti-microbial (biocidal) activity using a combination of 2-bromo-2-(bromomethyl)-glutaronitrile and 2-bromo-2-nitro-propane-1,3-diol. The methods and compositions of the invention are very effective in preventing microbial spoilage of latex carpet backing compounds and in paper and pulp preparation, particularly with respect to latex paper coatings. Compositions containing the active ingredients in ratios of from 0.0015 parts 2-bromo-2-(bromomethyl)-glutaronitrile to 1 part 2-bromo-2-nitro-propane-1,3-diol to 40 parts 2-bromo-2-(bromomethyl)-glutaronitrile to 1 part 2-bromo-2-nitro-propane-1,3-diol.

FIELD OF THE INVENTION

This invention relates to methods and compositions for obtainingsynergistic anti-microbial (biocidal) activity using a combination of2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane-1,3-diol. The methods and compositions of theinvention are very effective in preventing microbial spoilage of latexcarpet backing compounds and in paper and pulp preparation, particularlywith respect to latex paper coatings.

BACKGROUND OF THE INVENTION

Styrene/butadiene rubber latexes are used in adhesives for carpetbacking to prevent the unraveling of the carpet fibers and are also usedin the paper industry as coatings. One of the problems associated withthe latexes is microbial (particularly bacterial) contamination of theuncured latex. Several problems ensue when formulated latex coatings,adhesives, or backings become contaminated. These include an offensiveodor, which remains in the latex after it is cured and renders theresulting carpet or other product undesirable for use, changes inrheology of the adhesive or backing, which prohibit uniform coating of acarpet-back surface and make the viscosity of the adhesive or backingunsuitable for use, and reduced surface properties, which cause anadhesive or backing to lose strength and which can result indelamination of a carpet from its backing.

Contamination is most often noticed first by odor. When the microbialcount exceeds 100,000 microbes per ml, odor begins to become apparent.The offending microbes can include bacteria, fungi (and yeasts), algaeand other microscopic forms of life. Although yeasts and fungi canpresent problems, most problems in the spoilage of carpet backingcompounds are caused by bacteria. Gram-negative bacteria are ofparticular importance in this regard as they are generally viewed ascausing more degradation than gram-positive bacteria. For example,Pseudomonas aeruginosa, which is widely distributed in nature and isfound in the water, soil, and intestinal tract of man and animals andconsequently, is a commonly occurring bacterial contaminant. See "TestMethod D4783-89" published by the American Society for Testing andMaterials for further information concerning common contaminants.

Contamination of latex backing or adhesive can have several sources. Thefirst source may be the finished latex itself. If the latex is notproperly treated, it may introduce contaminants into the carpet millwhere it is formulated. The scrim adhesive-type latexes used in carpetbackcoatings are all carboxylated; the foam backing types (coldpolymerized SBR latex) are not. In some cases, contamination resultsfrom shipping or extensive storage of finished latex.

The second source of potential problems is the raw materials used withfinished latex. Typically, the styrene-butadiene latex backcoatings areheavily filled with calcium carbonate or clay, which are sources ofmicrobial contamination. Unsterilized water has also been used asdilution, washing or carrying agent. Many times recycled water is usedfor dilution of latex. The industry is moving towards recycling waterbecause of environmental, safety and economic concerns, and the recycledwater presents an ideal environment for microbial growth. Commonly addeddefoamers, surfactants and viscosifiers could also be bacteria carriers.

Another source of potential problems is the storage of compounded latex.Storage of the compounded latex in storage tanks where temperature andtime of storage are not strictly controlled all pose opportunities forintroduction and growth of bacteria.

In the past, latex suppliers have added microbicide to the latex tocontrol contamination in the carpet mills. Such microbicides include forexample, 1,2-benzoisothiazolin-3-one, which is sold by Imperial ChemicalIndustries under the trade name Proxel GXL, and a mix of5-chloro-2-methyl-4-isothiazolin-3one and 2-methyl-4-isothiazolin-3-one,which is sold by Rohm and Haas under the trade name Kathlon LX, and amix of 1,2-dibromo-2,4-dicyanobutane and 1,2-benzoisothiazolin-3-one,which is sold by Calgon under the trade name Biocheck 410. However,these products suffer from certain shortcomings. For example, highconcentrations of 1,2-benzoisothiazolin-3-one, are required toadequately preserve the latex.

Tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (Nalco 5787) andNalco 5793 have also been used in carpet backing adhesives. Nalco 5787is a preservative at high dosages but has odor problems and does notoffer quick kill capabilities. Nalco 5793 is a good quick kill biocidebut does not offer preservation. Therefore, it is apparent that animproved method and composition for inhibiting growth of microorganisms(and bacteria in particular) in latex backing formulations is needed.

Co-pending application No. 08/088,050, filed Jul. 7, 1993, now U.S. Pat.No. 5,385,605, (and incorporated herein by reference) discloses asynergistic composition comprising methylene(bisthiocyanate) and2-bromo-2-nitro-propane 1,3-diol. The inventor has now discovered thatcompositions containing 2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane 1,3-diol are also synergistic.

SUMMARY OF THE INVENTION

This invention provides a surprisingly efficacious combination usefulfor inhibiting microorganism growth, particularly in compositionscontaining latex, e.g., for use in carpet manufacture.

In particular embodiments the invention provides an anti-microbialcomposition comprising 2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane-1,3-diol in a ratio ranging from about 0.015parts 2-bromo-2-(bromomethyl)glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol to about 40 parts2-bromo-2-(bromomethyl)-glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol. In one embodiment, the compositioncontains at least 0.5 parts per million2-bromo-2-(bromomethyl)-glutaronitrile and at least 1.64 parts permillion 2-bromo-2-nitro-propane-1,3-diol, and, in a second embodiment,at least 4 parts per million 2-bromo-2-(bromomethyl)-glutaronitrile andat least 0.82 parts per million 2-bromo-2-nitro-propane-1,3diol. Morepreferably, the composition contains at least 16 parts per million2-bromo-2-(bromomethyl)-glutaronitrile and at least 3 parts per million2-bromo-2-nitro-propane-1,3-diol. An anti-microbial formulationcomprising 0.25 parts to 64 parts (more preferably from about 2 parts toabout 8 parts) of a dispersion containing about 25% 2-bromo-2-(bromomethyl)-glutaronitrile as the active ingredient to about onepart of an aqueous solution containing about 41%2-bromo-2-nitro-propane-1,3-diol is also included. The ratio of thedispersion to the aqueous solution may also be four parts to one part.Tektamer 38, Calgon Corp., Pittsburgh, Pa., may be used as thedispersion and Nalco 5780 may be used as the solution.

The invention also provides a method for inhibiting microbial growth ina composition that contains a latex. The method includes the step ofadding to the composition 2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane-1,3-diol in a ratio ranging from 0.15 parts2-bromo-2-(bromomethyl)glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol to 40 parts2-bromo-2-(bromomethyl)-glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol, in amounts of each which incombination, are effective to inhibit microbial growth. In oneembodiment, the amount of 2-bromo-2-(bromomethyl)-glutaronitrile is atleast 0.5 parts per million and the amount of2-bromo-2-nitro-propane-1,3-diol is at least 1.64 parts per million. Inanother embodiment, the amount of 2-bromo-2-(bromomethyl)-glutaronitrileis at least 4 parts per million and the amount of2-bromo-2-nitro-propane-1,3-diol is at least 0.82 parts per million, andin adapted for handling higher contamination levels, the amount of2-bromo-2-(bromomethyl)-glutaronitrile is at least 16 parts per millionand the amount of 2-bromo-2-nitro-propane-1,3-diol is at least 3 partsper million. Among other things, the methods of the invention may beused to treat uncured latex compounds formulated for use as a carpetbacking or adhesive or for use as a paper coating. A composition for useas a carpet backing comprising latex, water, a filling agent (such asground limestone or calcium carbonate), and2-bromo-2-(bromomethyl)glutaronitrile and2-bromo-2-nitro-propane-1,3-diol in amounts of each that, incombination, are effective to inhibit microbial growth in the latex isalso claimed.

DESCRIPTION OF THE DRAWINGS

FIG. 1 representation of a microtiter plates in which a combination ofTektamer 38 and Nalco 5780 showed synergistic biocidal activity againsta culture of wild bacteria in latex-containing medium. Shaded squaresrepresent wells of the plate in which bacterial contamination wasdetected by a change of color (from dark purple to bright pink) in theculture medium.

FIGS. 2 and 3 are representations of microtiter plates in which Tektamer38 and Nalco 5780 showed synergistic activity against a culture ofPseudomonas aeruginosa in a latex containing medium. Shaded squaresrepresent wells of the plate in which bacterial contamination wasdetected by a change of color (from dark purple to bright pink) in theculture medium.

FIG. 4 is a representation of a microtiter plate in which Tektamer 38and Nalco 5780 showed synergistic activity against a wild culture in alatex containing medium. Shaded squares represent wells of the plate inwhich bacterial contamination was detected by a change of color (fromdark purple to bright pink) in the culture medium.

DETAILED DESCRIPTION OF THE INVENTION

The synergistic anti-microbial composition of the present invention mayfind utility in a variety of applications in which biocides are commonlyused including, e.g., applications in industries that make or use paper,wood and pulp and their products and in the latex industry, e.g., inpreparation of paints and other coatings. However, a particularlyimportant contribution of the synergistic anti-microbial composition isto the carpet industry, to prevent purification of latex carpet backing.Accordingly, without limiting the invention in any way, the use of thesynergistic anti-microbials of the present invention in this context isdescribed below.

In a preferred embodiment, a synergistic combination of2-bromo-2-(bromomethyl)-glutaronitrile ("BBMG") and2-bromo-2-nitro-propane-1,3-diol ("BNPD") is used for protection of alatex adhesive or backing formulated for use with a carpet or carpettile product. The combination of these agents may be used in protectionof any of a number of latex-adhesive formulations used in the carpetindustry. Examples of polymers and copolymers that may be used in thelatex base include, for example, vinyl acetate-ethylene,styrene-butadiene, vinylidene chloride, vinyl chloride, celluloseacetate butyrate, vinyl chlorideacrylonitrile, vinyl acetate-acrylicacid, vinylidene-chlorideacrylonitrile, acrylic acid-methacrylic acid,butadieneacrylonitrile, acrylic acid-styrene, acrylonitrile-styrene,acrylonitrile-acrylic acid, acrylonitrile-alkyl acrylate, vinyl acetateacrylate ester, acrylonitrile butadiene styrene and others.

The active agents can be added directly to the latex base used toformulate the compounded latex adhesive or backing. In addition, thecompounds can be added to the latex mixture at any of a number of pointsin the production process, e.g., in line as the mixture delivered to thetank for compounding, in the compounding chamber, in line as the mixtureis delivered from the compounding chamber to a storage tank, or in thestorage tank itself. Preferably, the agents are added before latex iscured, and more preferably before compounded latex is applied to thecarpet, since microbial contamination usually occurs prior to this step.In some embodiments, each of the synergistic agents is added separatelyand is allowed to mix with the latex at the point of addition orthereafter. Alternatively, the synergistic agents may be formulatedtogether and added as a single ingredient at any of the points describedabove.

The synergistic combination of BBMG and BNPD has been shown to beeffective over a wide range of concentrations and compound ratios. Ingeneral, however, it is preferred to add the components in an amountsufficient to produce final concentrations in the compounded latexranging from at least about 0.5 ppm BBMG and more preferably from atleast about 4 ppm BBMG, and from at least about 1 ppm BNPD and morepreferably from at least about 3 ppm BNPD. Higher concentrations of theactive ingredients (e.g., to about 250 ppm BBMG and 150 ppm BNPD) can beused depending on the extent of contamination and the conduciveness ofthe particular environment to microbial growth. One may use a wide rangeof ratios of active ingredients, e.g., ratios ranging from about 0.15parts BBMG to 1 part BNPD to about 40 parts BBMG to 1 part BNPD. Morepreferred are compositions containing from about 1 part BBMG to 1 partBNPD. Compositions containing the components at a 1 to 1 ratio, 1.64(i.e. about 2) parts of a preparation containing 25% BBMG (e.g. Tektamer38) and one part of a preparation containing about 41% BNPD (e.g., Nalco5780) are especially preferred for use in the instant invention. Thoseof skill in the art, with the aid of the present disclosure, should beable to determine optimal effective concentrations and ratios to be usedfor a particular application.

If desired, the synergistic biocides may be formulated together prior touse and delivered as a single reagent. In certain instances, it may bedesirable to add solubilizing or emulsifying agents such as surfactants,ethylene glycols, etc., to formulate or emulsify a combined composition.The present inventor has found, for example, that a formulationcomprising 4 parts of Tektamer 38 (25% BBMG in a dispersing formula) and1 part of Nalco 5780 (a 41% solution of BNPD in a solvent containingfrom about 40-70% and generally about 44% dipropylene glycol monoethylether in water) produces a stable dispersion and a formulation suitablefor use as part of the present invention. A formulation containing 1part Nalco 5780 to 2 parts Tektamer 38 is also stable. Similarly, a 1 to1 mixture of Tektamer 38 and 5780 provides a formulation that is lessstable but can be used with agitation to insure suspension of the activeingredients prior to use. Other formulations suitable for convenientstorage and delivery of the synergistic biocides of the invention can beprepared according to known formulation technology by those of ordinaryskill in the art.

PRACTICAL EXAMPLE

Without limiting the invention in any way, the following exampleillustrates one method for application of the synergistic biocidalcomposition in the latex industry. A composition comprising acarboxylated styrene butadiene latex at 25% by weight is mixed withwater at 7% by weight, and a trace of a surfactant or dispersant such asCF1885, sold by Chemtex, Charlotte, N.C., and a vicosifier such asParagum 178 sold by Southern Inc., Simpsonville, S.C., are added withmixing. Ground limestone, e.g., as sold by Frank Glenn IndustrialMinerals, Dalton, Ga., in about 66 parts by weight is then compoundedwith the mixture. To this mixture is added an amount of BBMG and BNPD,(preferably at a ratio of about 1 part of BBMG to 1 part of BNPD) (or,if Tektamer 38 and Nalco 5780 are used, about 1.64 parts of Tektamer 38to 1 part of compound 5780), effective to produce a biocidalconcentration in the mix, e.g. from at least about 0.5 ppm to 250 ppmBBMG and about 0.5 to 150 ppm BNPD. The formulated latex may then bepumped to storage and held until needed and then applied to the carpetbacking by any of the number of standard techniques, including forexample, spraying, spreading, etc. The processed carpet is rolled to aheat dryer where the latex backing is cured and may be processed furtheraccording to standard techniques in the art.

EXPERIMENTAL EXAMPLES

The experimental examples below demonstrate the synergistic activity ofBBMG and BNPD in inhibiting microbial growth in latex as measured by atest for biocide assessment. The test is described in co-pending U.S.patent application Ser. No. 07/670,858, filed Mar. 18, 1991, nowabandoned by Linda R. Robertson and in U.S. patent application Ser. No.08/088,050 by Allen R. Syrinek filed Jul. 7, 1993, now U.S. Pat. No.5,385,605 both of which are incorporated herein by reference.

The test uses a commercially available reduction-oxidation indicator(resazurin) which changes color from purple to pink in the presence ofactively respiring microorganisms. The method used in the examplesdescribed below actually contained two separate tests: (1) a method fordetermining minimum inhibitory concentration (MIC) for a single biocide,and (2) a method for demonstrating that the claimed combination of BBMGand BNPD was synergistic. Test 1 used serial dilutions of singlemicrobicide in the presence of nutrient and indicator. Test 2 uses thesame principle of test 1, but uses a number of samples containingdifferent concentrations of BBMG and BNPD. The samples are arranged in agrid (i.e., in the wells of a 96-well microtiter culture plate).Usually, the grid contains high concentrations of biocide A on the topgoing to lower concentrations of biocide A on the bottom; and highconcentrations of biocide B on the right going to low concentrations ofbiocide B on the left. Each biocide is blended with the other over thegrid.

To perform the test a nutrient mixture ("solution 1") containing 0.10 gdextrose, 0.80 g nutrient broth (beef extract with peptone), 0.25 gnondairy creamer (Carnation Coffee-Mate™), 22 milligrams of resazurin,0.10 g KH₂ PO₄, 0.10 g Na₂ HPO₄, and 100 ml sterile water is prepared.This solution is then mixed with an equal volume of base latexcontaining a test organism or culture to produce a nutrient/latex medium("solution 2"). In the experiments discussed below, the latex wasobtained from the Goodyear Chemical Company and had not been treatedwith any anti-microbial compounds. Solution 2 is then used as a diluentfor the product to be tested. For example, a stock mixture containing2000 ppm Tektamer 38 and another stock mixture containing 2000 ppm ofNalco 5780 were prepared in solution 2.

Typically, a serial dilution of the contaminated latex (withoutbiocides) is performed in column 11 of the plate in order to assess theextent of contamination of the latex. Wells in column 11 are filled with125 microliters of solution 1, then 125 microliters of the contaminatedlatex is placed in well All and 1:2 serial dilutions of the latexmixture into solution 1 are made in the remaining wells of column 11.When this test is performed, well All contains the concentration ofcontaminated latex/solution 1 present in the wells of columns 1-10 and12. The remaining wells in column 11 contain 1:2 serial dilutions of thecontaminated latex solution.

The test to determine the MIC of a single agent is performed in column12 of a 96-well plate for biocide A and column 1 of the plate forbiocide B. A solution containing the desired concentration of biocide Ais made by mixing the appropriate volume of the 2000 ppm biocidesolution with the appropriate volume of solution 2. A solutioncontaining the desired concentration of biocide B is made similarly.Next, 125 microliters of solution 2 is placed in each well of columns 1and 12. Then, 125 microliters of the biocide A preparation is added towell A12 and mixed with the latex. A 125 microliter aliquot from wellA12 is added to well B12 and mixed. This procedure is repeated down thecolumn until well H12 has been dosed with biocide, and 125 microlitersis discarded from well H12. Biocide B is serially diluted in column 1 ina similar manner. The MIC for each biocide is indicated by the lowestconcentration of the biocide effective to prevent microbial growthsufficient to cause a color change in the nutrient/latex medium.

In order to test for synergy, the biocides are mixed over a range ofratios and concentrations. Eight channels of a 12 channel Eppendorfpipet are used to place 125 microliters of solution 2 in each well incolumns 2-10. The pipet is then rinsed. Eight channels of the pipet arethen used to place 125 microliters of a desired concentration of biocideA in each well of column 10. The pipet is then used to make 2-foldserial dilutions from column 10 to column 2. This produces aconcentration gradient for biocide A which goes from the startingconcentration (in column 10) to a much lower final concentration in thelast column used (e.g. in column 2). Now biocide B at 2(X) of a desiredconcentration (X), is prepared in solution 2 and 125 microliters of thisis pipetted into row A of columns 2-10, and mixed with the 125 μl oflatex in the well to give a 1:2 dilution of the biocide and produce afinal biocide B concentration of X. Next a 1X solution of biocide B insolution 2 is prepared and 125 microliters is placed into row B ofcolumns 2-10, and mixed to produce a final biocide concentration of0.5X. This procedure is repeated on rows C-H in columns 2-10 atconcentrations of 0.25X, 0.125X, 0.0625X, etc. This procedure alsodilutes the concentration of biocide A by 50%.

The plates are sealed with tape and incubated for twentyfour hours at37° C. The plates are then visually examined and the data reflectingwell color changes are recorded. A color change from violet blue to pinkis indicative of microbial contamination. The minimum inhibitoryconcentration (MIC) of each biocide alone, i.e., the lowestconcentration at which no color change was observed, is then recorded.Similarly, for the wells containing mixtures, the concentration of firstand second biocides in each well where no color change was observed isrecorded. Synergy is then calculated as follows is calculated accordingto the formula: ##EQU1##

Qa is the quantity of biocide in the admixture;

QA is the MIC of biocide A;

Qb is the quantity of second biocide in the admixture; and

QB is the MIC of biocide B.

The value of X is then determined. If X is less than one, a synergisticcomposition is present; if X is equal to one, an additive combination ispresent, and if X is greater than one, an antagonistic composition ispresent. Understanding of this procedure may be further facilitated byreference to Kull et al., Applied Microbiology 9:538-554 (1961) and toU.S. Pat. No. 4,661,518 issued Apr. 28, 1987 to LaMarre et al.

EXPERIMENTAL EXAMPLE 1

In this example, a mixed wild culture obtained from a batch ofcontaminated latex was used as the inoculum to produce a startingcontamination level of about 10⁵ -10⁷ cells/well. Tektamer 38 (whichcontains 25% 2-bromo-2-(bromomethyl)glutaronitrile as an activeingredient) and Nalco 5780 (which contains 41%2-bromo-2-nitro-propane-1,3-diol in an aqueous solution with about 44%percent by weight dipropylene glycol monoethyl ether) were used assources of the active biocides at the concentrations shown in FIG. 1.The results of this experiment are shown in FIG. 1.

In this experiment, synergistic biocidal activity was observed at 0.5ppm BBMG and 3.28 ppm BNPD, at 1 ppm BBMG and 3.28 ppm BNPD, at 2 ppmBBMG and 3.28 ppm BNPD, at 4 ppm BBMG and 3.28 BNPD, at 8 ppm BBMG and3.28 ppm BNPD, at 16 ppm BBMG and 3.28 BNPD, at 16 ppm BBMG and 1.64 ppmBNPD, at 31.25 ppm BBMG and 1.64 BNPD, and at 31.25 ppm BBMG and 0.82ppm BNPD. Therefore in this experiment, synergy was observed over a widerange of BBMG:BNPD ratios, ranging from as little as about 0.15:1 toabout 40:1, which corresponds to a range of from about 0.250 partsTektamer 38 to 1 part Nalco 5780 to about 64 parts Tektamer 38 to 1 partNalco 5780.

EXPERIMENTAL EXAMPLE 2

In this example, a culture of Pseudomonas aeruginosa (available from theAmerican Type Culture Collection, Rockville, Md., under deposit number10145) was used as the inoculum. An aliquot of the seed culture wasadded to a latex nutrient mixture to produce a bacterial level of about10⁵ -10⁷ cells/well and tested as described above. Tektamer 38 and Nalco5780 were used as biocides. The results of this experiment are shown inFIG. 2.

In this experiment, synergistic biocidal activity was observed at 2 ppmBBMG and 1.64 ppm BNPD, and at 4 ppm BBMG and 0.82 ppm BNPD. Thereforein this experiment, synergy was observed over a wide range of BBMG:BNPDratios, ranging from as little as about 1:1 to about 5:1, whichcorresponds to a range of from about 2 parts Tektamer 38 to i part Nalco5780 to about 8 parts Tektamer 38 to 1 part Nalco 5780.

EXPERIMENTAL EXAMPLE 3

In this example, a culture of Pseudomonas aeruginosa (available from theAmerican Type Culture Collection, Rockville, Md., under deposit number10145) was used as the inoculum. An aliquot of the seed culture wasadded to a latex nutrient mixture to produce a bacterial level of about10⁵ -10⁷ cells/well and tested as described above. Tektamer 38 and Nalco5780 were used as biocides. The results of this experiment are shown inFIG. 3.

In this experiment, synergistic biocidal activity was observed at 1 ppmBBMG and 3.28 ppm BNPD, at 2 ppm BBMG and 3.28 ppm BNPD, at 4 ppm BBMGand 3.28 ppm BNPD, at 8 ppm BBMG and 3.28 BNPD, and at 16 ppm BBMG and1.64 ppm BNPD. Therefore in this experiment, synergy was observed over awide range of BBMG:BNPD ratios, ranging from as little as 3:1 to 10:1,which corresponds to a range of from about 0.5 part Tektamer 38 to 1part Nalco 5780 to about 16 parts Tektamer 38 to 1 part Nalco 5780.

EXPERIMENTAL EXAMPLE 4

In this experiment a wild culture was used as inoculum (about 10⁵ -10⁷cells/well) and Tektamer 38 and Nalco 5780 were used as biocides.

In this experiment, synergistic biocidal activity was observed at 16 ppmBBMG and 3.28 ppm BNPD, and at 31.25 ppm BBMG and 1.64 ppm BNPD.Therefore in this experiment, synergy was observed over a wide range ofBBMG:BNPD ratios, ranging from as little as about 5:1 to 20:1, whichcorresponds to a range of from about 8 parts Tektamer 38 to 1 part Nalco5780 to about 33 parts Tektamer 38 to 1 part Nalco 5780.

The foregoing description of the invention has been directed toparticular preferred embodiments in accordance with the requirements ofthe patent statutes and for purposes of explanation and illustration. Itwill be apparent, however, to those skilled in the art that manymodifications and changes may be made without departing from the scopeand the spirit of the invention.

For example, numerous methods for formulating and using the synergisticanti-microbial agents may be used. In addition, the anti-microbialagents may be used in a wide variety of applications not specificallymentioned here. It is apparent that the invention may also be utilized,with suitable modifications within the state of the art. It is theApplicant's intention in the following claims to cover all suchequivalent modifications and variations which fall within the truespirit and scope of the invention.

What is claimed is:
 1. An anti-microbial composition comprisingsynergistic effective amounts of 2-bromo-2-(bromomethyl)-glutaronitrileand 2-bromo-2-nitro-propane-1,3-diol in a ratio ranging from 0.15 parts2-bromo-2-(bromomethyl)glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol to 40 parts2-bromo-2-(bromomethyl)-glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol.
 2. The composition of claim 1 whereinthe composition contains at least about 0.5 parts per million2-bromo-2-(bromomethyl)glutaronitrile and at least 1.64 parts permillion 2-bromo-2-nitro-propane-1,3-diol.
 3. The composition of claim 1wherein composition contains at least about 0.4 parts per million2-bromo-2-(bromomethyl)glutaronitrile and at least 1 parts per million2-bromo-2-nitro-propane-1,3-diol.
 4. The composition of claim 1 whereinthe composition contains at least about 16 parts per million2-bromo-2-(bromomethyl)glutaronitrile and at least 3 parts per million2-bromo-2-nitro-propane-1,3-diol.
 5. An anti-microbial formulationcomprising synergistic effective amounts of between 1 and 4 parts of aformulated dispersion of about 25%2-bromo-2-(bromomethyl)-glutaronitrile to about one part of solutioncontaining about 41% 2-bromo-2-nitro-propane-1,3-diol.
 6. Theformulation of claim 5 wherein the ratio of said dispersion to saidsolution is about 2 parts to 1 part.
 7. The formulation of claim 5wherein said emulsion comprises about 25%2-bromo-2-(bromomethyl)-glutaronitrile in formulated dispersion.
 8. Theformulation of claim 5 wherein said solution comprises dipropyleneglycol monoethyl ether and about 41% 2-bromo-2-nitro-propane-1,3-diol.9. A method for inhibiting microbial growth in a composition thatcontains a latex comprising adding to the composition2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane-1,3-diol in a ratio ranging from about 0.15parts to 1 part 2-bromo-2-nitro-propane-1,3-diol to 40 parts2-bromo-2-(bromomethyl)-glutaronitrile to 1 part2-bromo-2-nitro-propane-1,3-diol in synergistic effective amounts ofeach which in combination, are effective to inhibit microbial growth.10. The method of claim 9 wherein the amount of2-bromo-2-(bromomethyl)-glutaronitrile is at least about 0.5 parts permillion and the amount of 2-bromo-2-nitro-propane-1,3-diol is at leastabout 1.64 parts per million.
 11. The method of claim 9 wherein theamount of 2-bromo-2-(bromomethyl)-glutaronitrile is at least about 0.4parts per million and the amount of 2-bromo-2-nitro-propane-1,3-diol isat least about 1 part per million.
 12. The method of claim 9 wherein theamount of 2-bromo-2-(bromomethyl)-glutaronitrile is at least about 16parts per million and the amount of 2-bromo-2-nitro-propane-1,3-diol isat least about 3 parts per million.
 13. The method of claim 9 whereinsaid latex composition is an uncured latex compound formulated for useas a carpet backing or adhesive.
 14. Method of claim 9 wherein saidlatex composition is an uncured latex composition formulated for use asa paper coating.
 15. A composition for use as a carpet backingcomprising:a) latex; b) water; c) a filling agent; and d)2-bromo-2-(bromomethyl)-glutaronitrile and2-bromo-2-nitro-propane-1,3-diol in synergistic effective amounts ofeach, which in combination, are effective to inhibit microbial growth insaid latex.